Cold extrusion method



June 17, 1969 a. T. WOODLE COLD EXTRUSION METHOD Filed April 30, 1965 FIG. I.

BILLY TED WOODLE INVENTOR.

'ATTORNE Y United States Patent U.S. Cl. 72-254 3 Claims ABSTRACT OF THE DISCLOSURE The method of cold forming a blank of ductile metal into a cup shaped article having an opening of reduced transverse dimension in the bottom thereof, the steps of placing said blank in an open cavity of a die, forcing a punch into said blank to form a hollow and at the same time extrude the displaced metal a distance along said punch, placing the partially formed blank in a second die having a die opening in the bottom thereof, inserting a punch into the hollow of said partially formed blank and removing metal through the hole of the die, and further enlarging the hollow in the blank and further elongating the same by forcing an enlarged punch therein.

This invention relates to cold forming of steel and has reference to extruding cup shaped articles having single openings of reduced diameter in their otherwise closed ends.

The primary object of the invention is to provide a method of forming an article such as described with a press of considerably less tonnage than heretofore required for that purpose.

Another object is to provide a method which requires only two steps to form the described article.

Another object is to provide a method for the described purpose wherein the article being formed is elongated to its full length and size during the second and final forming step.

Another object is to employ compression forces only on the article being formed so as to provide greater strength and soundness in the finished product.

These and other objects of the invention will become apparent from the following description and the accompanying drawing, in which:

FIGURE 1 is a perspective view of a steel blank cut from round stock from which the article is formed.

FIGURE 2 is a vertical sectional and broken elevational view of a die and punch, and showing the article in section as it appears at the end of the first forming step.

FIGURE 3 shows a vertical sectional view of second die and punch at the beginning of the second step.

FIGURE 4 is a view of the same die and punch illustrated in FIGURE 3, but showing the punch at the end of its operation and the completed article in section.

FIGURE 5 is a broken perspective view of the completed article.

The blank is any suitable cylindrical piece of steel which may be cut from round stock and which may be somewhat out of round. By way of example, but not as a limitation, C-l018 and C-4140 steel have been used successfully when performing the present method.

The blank 10, which is of predetermined volume, is placed in the cylindrical cavity 11 of a die 12, which die includes a knock-out bar 13 in its lower axial center. The diameter of blank 10 is slightly less than the diameter of the cavity 11 so that the blank is readily received, and the depth of the cavity is such that the blank is initially fully received therein.

A cylindrical punch 14 is mounted in a press, not

'ice

shown, in the usual manner. The die 12 is also supported in the usual manner, but it is pointed out that the punch 14, within practical limits, is concentric with the die cavity. For reasons which will become apparent, the diameter of the cavity 11, and the resulting outside diameter of the first formed stage of the article is less than the outside diameter of the finished article, to be described. The punch 14, in the first step, is forced downwardly into the top of the blank 10, and which movement is continued until a partially completed cup-shaped article 10a results. It is to be noted that the partly formed article 10a is subjected to compression forces only during the forming operation, and that the metal displaced by the punch 14 is extruded upwardly along the length of the punch. If necessary, the knock out bar 13 may be used to remove the partially completed article 10a from the die 12.

The second punching and extruding operation is initiated as illustrated in FIGURE 3. The partially completed article 10a is placed in the cavity 16 of a second die 17. As before, the metal to be formed, 10a is fully received in the cavity 16 and is, initially, a loose fit therein. The punch 18 of the second operation has a lower diameter 19 slightly less than the diameter of the first described punch 14, and the upper diameter 20 of the punch is of substantially the same as the largest inside diameter of the finished article 10b to be formed. The shoulder 21 between the two punch diameters is designed so as to compress and flow a portion of the metal laterally during the second forming operation.

There is a die opening 22 in the bottom of the die 17 concentric with the cavity 16 for punching out a slug 23 (FIGURE 4) prior to completing the second metal forming operation. For this reason the small diameter 19 of the second punch 18 is longer than the depth of the cavity in partially formed article 10a.

As before, the punch 18 is forced downwardly, and the metal being formed is compressed, and a portion of which is forced upwardly around the large diameter 20. As best shown in FIGURE 4, the travel of the punch 18 stops short of the large diameter 20 reachin the bottom of the die cavity 16, thus leaving a partially closed end in the finished article 10b. The small diameter 19 of the punch 20 maintains the size of the opening 24 throughout the second forming operation. Not shown, strippers may be used after each forming operation to remove the partially formed article 10a and the finished article 10b from the punches 14 and 18. Machining may be per formed on the finished article 10b, for example, threads may be cut where desired.

The invention is not limited to the exact method herein shown and described, but may be varied within the scope of the appended claims.

What is claimed is:

1. The method of cold forming a blank of ductile metal into a cup shaped article having an opening of reduced transverse dimension in the bottom thereof, the steps of placing said blank in an open cavity of a die, forcing a punch into said blank to form a hollow and at the same time extrude the displaced metal a distance along said punch, placing the partially formed blank in a second die having a die opening of reduced diameter in the bottom thereof, inserting a punch having an extending end of a size to penetrate said opening of reduced diameter into the hollow of said partially formed blank and removing metal through the last said opening of the die, and further enlarging the hollow in the blank and further elongating the same by forcing an enlarged punch therein.

2. The method defined in claim 1, and wherein said blank and said partially formed blank are initially fully received within their respective dies.

3 3. The method defined in claim 1, and wherein the opening in the bottom of the partially formed blank in the second die is supported against the flow of metal inwardly of said opening.

References Cited UNITED STATES PATENTS 4 6/1936 Lorant 72-254 2/ 1965 Williams 72-267 X US Cl. X.R. 

